WINNIPEG -- A study suggests older kids counselling younger kids in nutrition and activity can reduce childhood diabetes by at least 15 per cent.

The year-long study showed children could reduce their waist size by 1.42 centimetres -- taking into account normal growth over a school year -- because they'll tune in to the advice of their school's oldest students.

One centimetre less on a child's waistline "can translate into 15 per cent long-term difference in diabetes," Jonathan McGavock, a professor of pediatrics and child health at the University of Manitoba, said Monday.

"Small changes lead to big changes in overall health. Overweight kids, they might experience three to four centimetres" less on their waistline, said McGavock, who is also a research scientist at the Manitoba Institute of Child Health.

The study by the University of Manitoba and provincial government was conducted in the 2009-2010 school year in 19 randomly selected schools with 647 randomly selected students.

It was published in JAMA Pediatrics, a journal of the American Medical Association.

McGavock conducted the research with Robert Santos, a community health scientist who is with Healthy Child Manitoba and a professor at the University of Manitoba.

The pair came up with a "Healthy Buddies" curriculum on older kids advising younger kids on personal health. Teachers taught the older kids the information, then the older kids took it to the younger kids once a week, for talks and intense fitness activity.

The idea worked in British Columbia, said McGavock.

"They developed a curriculum that healthy messages coming from older children would be taken up more effectively than if they came from teachers or health care professionals."

It's the same principle as when older kids read to younger kids to encourage literacy, or any number of mentoring programs in which older students bond with younger, McGavock said.

Each school chose a Grade 5 or 6 class to mentor a Grade 2 or 3 class, said McGavock. The only criterion was that the school neither pick out all the athletes nor the overweight kids.

"A big component was feeling good at any size," he said. "Be comfortable with your own body weight."

The researchers will not name the schools involved, but they included remote northern First Nations schools, some in inner city Winnipeg and an affluent part of the city, and a mixture of rural schools.

Even where availability and affordability of nutritious food were issues, McGavock said, "it still had an effect."

McGavock said he and Santos will present their findings to the province, which could develop a larger peer mentoring program.

Meanwhile, tracking those children's waist sizes has not been possible, but child health officials are compiling data on the 647 students -- without knowing individual names -- on their health compared to the population their age.

"We can look at visits to doctors, to hospitals, their medications," said McGavock.

Gordon Bell High School principal Arlene Skull, a home economist whose school has employed a professional chef for several years, applauded the idea.

Gordon Bell has had great success with its free breakfast program by encouraging varsity and junior varsity athletes to grab a plate and glass of milk after before-school practice, Skull said. Younger students in the Grades 7 to 12 school now think free breakfast is cool.

"They look up to the kids on the teams," Skull said. "You get these big dudes and wonderful girls go in and eat a healthy breakfast. It's a good place to be. Having them go into the cafeteria encourages the younger children that this is an OK thing and not a stigma," Skull said.

"Kids obese on their 18th birthday are more likely to be obese as adults," said Dr. Randy Fransoo, a researcher with the Manitoba Centre for Health Policy.